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From: Alex =?utf-8?Q?Benn=C3=A9e?= <alex.bennee@linaro.org>
In-reply-to: <121c5948-5cab-f4b7-d88b-0fe4d689c474@twiddle.net>
Date: Thu, 08 Dec 2016 20:38:47 +0000
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Subject: Re: [Qemu-devel] [PATCH v4 23/64] tcg: Allow an operand to be
 matching or a constant
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To: Richard Henderson <rth@twiddle.net>
Cc: qemu-devel@nongnu.org


Richard Henderson <rth@twiddle.net> writes:

> On 12/08/2016 09:19 AM, Alex Bennée wrote:
>>
>> Richard Henderson <rth@twiddle.net> writes:
>>
>>> This allows an output operand to match an input operand
>>> only when the input operand needs a register.
>>>
>>> Signed-off-by: Richard Henderson <rth@twiddle.net>
>>
>> It's hard to offer anything more than a mechanical review for this as
>> the constraints aren't intuitive to me (I guess not as a gcc hacker!).
>
> It's even more confusing for a gcc hacker, as we don't have a concept of
> alternatives.  You get one set of constraints.
>
>> Could we either expand the documentation of constraints in tcg/README
>> with a summary of the global ones?
>
> There's only one global constraint: 'i'.  So... sure, but I don't know how much
> that will help.

So what do 0..9 and & mean? Or do you mean they are only constraints
applied by the backend?

--
Alex Bennée